Sealant composition
A one-part room temperature vulcanisable (RTV) silicone composition containing a catalyst comprising (i) a titanate and/or zirconate and (ii) a metal carboxylate salt which cures to a silicone elastomer which may be used as a clear sealant which avoids discolouration and loss of adhesion upon aging.
1. A one-part room temperature vulcanisable (RTV) silicone composition comprising:
(a) an organopolysiloxane polymer having at least two hydroxyl or hydrolysable groups per molecule and of the general formula
in which each X is independently a hydroxyl group or a hydrolysable group, each R is an alkyl, alkenyl or aryl group, each R 1 is an X group, alkyl group, alkenyl group or aryl group and Z is a divalent organic group; d is 0 or 1, q is 0 or 1 and (d+q)=1; n is 0, 1, 2 or 3, y is 0, 1 or 2, or optionally y is 2, and z is an integer such that organopolysiloxane polymer (a) has a viscosity of from 10,000 to 75,000 mPa's at 25° C., or optionally from 10,000 to 60,000 mPa·s at 25° C.;
(b) a reinforcing filler comprising or consisting of fumed or pyrogenic silica filler which is optionally hydrophobically treated, in an amount of from about 5 to about 25 parts by weight per 100 parts by weight of organopolysiloxane polymer (a);
(c) a silane adhesion promoter, in an amount of from about 0.10 to about 2.0 parts by weight per 100 parts by weight of organopolysiloxane polymer (a); and
(d) a catalyst comprising (i) a titanate and/or zirconate and (ii) a metal carboxylate salt in an amount of from about 0.33 to 5.3 parts by weight per 100 parts by weight of organopolysiloxane polymer (a); and optionally, further comprising:
(e) a cross-linker; and/or
(f) a hydroxy scavenging agent selected from a disilazane or polysilazane.
2. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein organopolysiloxane polymer (a) is of the general formula
wherein n is 0 or 1, each of R, Z, R 1 , y, and z is as defined above, and each X is an alkoxy group.
3. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the titanate (i) is selected from the group consisting of tetra-n-butyl titanate, tetra-isopropyl titanate, tetra-(2-ethylhexyl) titanate, and combinations thereof, and optionally wherein catalyst (d) is chelated.
4. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the metal of the metal carboxylate salt (ii) is selected from the group consisting of zinc, aluminium, bismuth, zirconium, and combinations thereof.
5. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the metal carboxylate salt (ii) and is selected from the group consisting of zinc (II) carboxylates, aluminium (III) carboxylates, bismuth (III) carboxylates, zirconium (IV) carboxylates, zinc (II) alkylcarboxylates, aluminium (III) alkylcarboxylates, bismuth (III) alkylcarboxylates, zirconium (IV) alkylcarboxylates, and combinations thereof.
6. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the metal carboxylate salt (ii) and is selected from the group consisting of zinc ethylhexanoate, bismuth ethylhexanoate, zinc stearate, zinc undecylenate, zinc neodecanoate, and iron (III) 2-ethylhexanoate.
7. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the titanate and/or zirconate (i) and the metal carboxylate salt (ii) of catalyst (d) is provided in a molar ratio of 1:4 to 4:1.
8. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the composition comprises:
from 0 to 8 parts by weight of cross-linker (e) per 100 parts by weight of organopolysiloxane polymer (a); and
from 0 to 8 parts by weight of hydroxy scavenging agent (f) per 100 parts by weight of organopolysiloxane polymer (a);
provided at least one of components (e) or (f) is present.
9. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the composition additionally comprises one or more plasticisers.
10. A method of making the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , the method comprising mixing all of the ingredients together.
11. An elastomeric sealant material which is the cured product of the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 .
12. The elastomeric sealant material in accordance with claim 11 , which is a clear sealant.
13. A sealant suitable for use in the facade, insulated glass, window construction, automotive, solar and construction fields, wherein the sealant comprises or is formed from the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 .
14. A method for filling a space between two substrates so as to create a seal therebetween, the method comprising:
a) providing the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , and either b) or c);
b) applying the silicone composition to a first substrate, and bringing a second substrate in contact with the silicone composition that has been applied to the first substrate, or
c) filling a space formed by the arrangement of a first substrate and a second substrate with the silicone composition and curing the silicone composition.
15. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the (i) titanate and/or zirconate comprises tetra isopropyl titanate and the (ii) metal carboxylate salt comprises ethyl-hexanoic acid zinc.
16. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the (i) titanate and/or zirconate comprises tetra tertiary butyl titanate and the (ii) metal carboxylate salt comprises ethyl-hexanoic acid zinc salt.
17. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , wherein the (i) titanate and/or zirconate and the (ii) metal carboxylate salt of catalyst (d) is provided in a weight ratio of 2:1.
18. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1 , the (c) silane adhesion promoter is a reaction product of trimethoxymethylsilane, 3-aminopropyl trimethoxysilane, and glycidoxypropyl trimethoxysilane.